Electrophotographic printing method



1966 F. s. MACKLEM ELEQTRQPHOTOGRAPHIG PRINTING METHOD Original FiledMay 18, 1956 INVENTOR F. SUTHERLAND MflcKLs/w United States Patent3,288,6u ELECTRQPHOJTGGRAPHHC ERiNTlNG METHQD F Sutherland Maeklem, NewCanaan, Comp, assignor to Equipment Development Corp, New Canaan, Conn.Continuation of abandoned application Ser. No. 585,717, May 18, 1956.This application Nov. 19, 1965, Ser. No. 508,659

5 Claims. (Cl. 961) This application is a continuation of my copendingapplication, Ser. No. 585,717, filed May 18, 1956, now abandoned.

My invention relates to photoreproduction apparatus particularly adaptedto the employment of electrophotographic paper, film, or the like. Thisinvention incorporates certain improvements over that disclosed in myc0- pending application, Ser. No. 538,619, filed Oct. 5, 1955, nowabandoned.

It is an object of the invention to provide improved apparatus of thecharacter indicated and to provide an improved method for utilizingelectrophotographic paper, film, or the like.

It is another object to provide improved photoreproduction apparatus ofthe character indicated, whereby developed copies may be more quicklyand easily made.

It is a specific object to meet the above objects with a structureparticularly adapted to the efiicient reproduction of translucentmasters.

It is another specific object to meet the above objects with an improvedmethod and apparatus which permit full development and fixation of aprint while the master and print are held together, that is, beforeremoval of the master from the print,

Other objects and various further features of novelty and invention willbe pointed out or will occur to those skilled in the art from a readingof the following specification in conjunction with the accompanyingdrawings. In said drawings, which show, for illustrative purposes only,preferred forms of the invention:

FIG. 1 is a simplified sectional view illustrating important steps in mymethod and parts of my apparatus; and

FIGS. 2 and 3 are fragmentary diagrams representing alternatives forparts of the method and apparatus illustrated in FIG. 1.

Briefly stated, my invention contemplates photoreproduction apparatusadapted particularly to paper, film, or the like, having a coating whichis photosensitive when electrically charged. In the present invention, Iam specifically concerned with the improved use of such paper, film, orthe like, for reproduction of translucent masters, such as thoseprepared on tracing paper or vellum in ordinary drafting-shopprocedures. My invention features the development of the exposed copysheet while still held against the master through which exposure ismade. In this Way, I best assure retention of all charge developments upto and including the time of development (as by electrostatic dustingtechniques), and no separate handling is required of the copy sheet. Mymachine delivers the fully developed and fixed copy sheet Without everhaving separated the copy sheet from the master.

The process of photoreproduction is improved by feeding the photocopysheet and master into the machine and impressing a charge on oppositesides of both pieces of paper while they are together. Afterphotosensitizing by charging, the two sheets, if desired, may beretained together as mentioned above.

Referring to FIG. 1 of the drawing, my invention is shown in applicationto a photoreproduction apparatus in which a master sheet or tracing isfirst brought into register with a copy sheet 11, before introduction tothe 328855 Patented Nov. 29, 1966 machine at feed rolls 1213. Forconvenience, a table 14 is provided to facilitate assembly of the sheets10-11. Both sheets 10-11 are translucent, and the sheet 11 is of theelectrophotographic variety, meaning that it has on one side thereof acoating which is photosensitive when electrically charged. Forconvenience, throughout the specification and claims I shall refer tosuch paper, film, or the like 11 merely as paper, it being understoodthat such reference contemplates any vehicle suitable for the intendedpurpose and having a coating of the class described,

In the form shown in FIG. 1, the registered master sheet 10 and copysheet 11 are arranged with the coated side of the copy sheet 11 facingdownwardly on the table 14, and the master 10 is oriented for direct(unreversed) printing, that is, with the marked face thereof pressingdownwardly against the copy sheet 11. After passing through the feedrolls 1213, the sheets1911 are subjected to an electrostatic chargeregion, which in the form shown comprises spaced corona-dischargeelements 1546 on opposite sides of the sheets 1tl11. The charged sheetsare then preferably fed directly to a translucent cylinder 17 and areheld against the cylinder 17 by means of a belt 18 running with movementof the cylinder 17 so as to carry the master and copy sheets in thedirection indicated by the arrow 19.

The cylinder 17 is mounted for rotation about its axis and may be ofglass or translucent plastic, but for convenience throughout thisspecification, will be referred to as a glass cylinder, even thoughother materials will be understood to be contemplated by reference tothe cylinder 17 as a glass cylinder.

Within the cylinder 17 is a fixed light source 20 which is preferablydirectional and limited to essentially an elongated area substantiallycoextensive with the width of the copy sheet and located at essentiallyone angular location about the axis of the cylinder 17. The light source20 may be a fluorescent lamp, and shield 21 provides the desireddirectionality.

While in the form shown the exposed charged master and copy sheets 10-11are still held against each other and are advanced with movement of thecylinder 17, I provide means for developing the charge image whichresults on exposure. In the form shown, an electrostatic dusting brush22 is employed at a second fixed angular location about the axis of thecylinder 17. The brush 22 may be of cylindrical configuration andelongated in substantial conformity with elongation of light source 20.Brush 22 is shown to rotate continuously in a trough 23 having anaperture 24 adjacent the exposed coated surface of the copy sheet 11.Dusting material 25 is shown filling the trough 23, and an access door26 facilitates replenishment. Brush 22 is preferably driven at avelocity to achieve a small relative surface speed of the brush over theexposed coated surface of copy paper 11 as it passes the brush aperture24.

At a third fixed angular location about the axis of the cylinder 17, Ishow means 27 for fixing the developed image on paper 11. This operationmay be performed by application of heat to the coated surface of paper11 at an elongated aperture substantially coextensive with the exposedand developed width of the copy sheet 11. The heating means is shown toinclude an electrical heating element 28 and a blower 29. After fixing,the master and copy sheets are tangentially peeled off the roll 17 at3%. and feed-out rolls 31-32 discharge the original and the finishedcopy at an upper table 33, at which time the copy may be removed fromthe master,

The arrangements of FIGS. 2 and 3 are similar to FIG. 1 in that there isshown a feeding of a master and photocopy paper to a charging chamberwherein an electrical potential is impressed on opposite sides of themaster and photocopy paper.

The arrangement of FIG. 2 represents a slight modification'wherein but asingle corona-discharge element 15 is employed, preferably adjacent thecoated surface of the copy sheet 11. In order to establish a chargereference for the means 15, I show a single plate 35 adjacent the uppersurface of the master 10, and this plate may be referenced to groundpotential, as suggested at 36. If desired, the translucent cylinder 17'may be of the electrically conductive variety, as of electricallyconducting glass, and a brush element 37 assures maintenance of the sameground potential both on the plate 35 and on the cylinder 17'.

In the arrangement shown in FIG. 3, the translucent cylinder 17 is againof the electrically conductive variety, and reference of the potentialthereof to ground potential is suggested at 38. Electrostatic chargingof the sheets is accomplished at a corona-discharge element 39 fixedbetween the pulleys 4041 for the belt 18. Auxiliary pulleys 42-4344 areshown for routing the belt 18 around the charge element 39, so that thedesired charge development may be effected directly on the outer face ofthe copy sheet and with respect to the potential (ground) of thecylinder 17'. It will be noted that the charge element 39 is so locatedas to complete its charging function prior to exposure of the copy sheetto light from source 20.

It will be seen that I have described a relatively simplephotoreproduction apparatus, particularly applicable to the reproductionof translucent masters, such as engineering drawings on tracing paper,vellum, or the like. I have found that highly satisfactory reproductionscan be made even though the coating of the copy sheet faces away fromthe master sheet, and the fact that in accordance with my preferred formI perform development and fixing of the charged image prior toseparating the master from the copy sheet assures maximum retention ofelectrostatic charge images, so that more reliable results can beaccomplished than by the conventional method of facing the coatingagainst the master and separating the copy sheet from the master fordevelopment and fixing. Also, my method and apparatus permit directreproduction without reversal of the image from the master.

While I have described the invention in detail for the preferred formsshown, it will be understood that modifications may be made within thescope of the invention as defined in the claims which follow.

I claim:

1. The photo-reproduction method employing a sheet of translucent paperhaving a photoconductive insulative coating on one side thereof that isphotoelectricallyresponsive when subjected to an electrical charge,which comprises positioning a positive translucent master on theuncoated side of said sheet, impressing an electrical potential onopposite sides of said sheet and master while in contact with eachother, directing illumination through said master and sheet to thephotoconductive side thereof, thereby producing an electrical chargepattern corresponding to the copy on said master, and developing saidcoating while held in contact with said master by applying soliddeveloper particles to said photoconductive side, the particles adheringto the side in accordance with said charge pattern.

2. The photo-reproduction method employing a sheet Of translucent paperhaving a photoconductive insulative coating on one side thereof that isphotoelectricallyresponsive when subjected to an electrical charge,which comprises positioning a positive translucent master to theuncoated side of said sheet with the copy on said master lying adjacentsaid uncoated side, impressing an electrical potential on opposite sidesof said sheet and master while in contact with each other, directingillumination through said master and sheet to the photoconductive sidethereof, thereby producing an electrical charge pattern corresponding tothe copy on said master, electrostatically developing the resultingcharge pattern on the exposed coated surface while said sheet is held incontact with said master by applying solid developer particles to saidphotoconductive side, and heating said developer particles to fix theelectrostatic image while said sheet is held in contact with saidmaster.

3. The photo-reproduction method employing a sheet of translucent paperhaving a photoconductive insulative coating on one side thereof that isphotoelectrical1y-re sponsive when subjected to an electrical charge,which comprises positioning a positive translucent master on theuncoated side of said sheet, impressing an electrical potential onopposite sides of said master and sheet while in contact with eachother, directing illumination through said master to the photoconductiveside of said sheet, thereby producing an electrical charge patterncorresponding to the copy on said master, and developing said coating byapplying developer to said photoconductive side.

4. The photo-reproduction method employing a sheet of translucent paperhaving a photoconductive insulative coating on one side thereof that isphotoelectricallyresponsive when subjected to an electrical charge,which comprises positioning a positive translucent master on said sheet,impressing an electrical potential on opposite sides of said master andsheet while in contact with each other, directing illumination throughsaid master to the photoconductive side of said sheet, thereby producingan electrical charge pattern corresponding to the copy on said master,and developing said coating by applying developer to saidphotoconductive side.

5. The photo-reproducing method employing a sheet of translucent paperhaving a photoconductive insulative coating on one side thereof that isphotoelectrically-responsive when subjected to an electrical chargewhich comprises:

positioning a positive translucent master on the uncoated side of saidsheet;

impressing an electrical potential on opposite sides of said master andsheet while in contact with each other to charge substantially theentire area of said photoconductive coating of said sheet;

and, directing illumination through said master and sheet to thephotoconductive side thereof, thereby producing an electrical chargepattern corresponding to the copy on said master;

and developing said coating by applying solid developer particles tosaid photoconductive side, the particles adhering to the side inaccordance with said charge pattern;

and thereafter fixing said particles to said sheet.

No references cited.

NORMAN G. TORCHIN, Primary Examiner. C. E. VAN HORN, Assistant Examiner.

4. THE PHOTO-REPRODUCTION METHOD EMPLOYING A SHEET OF TRANSLUCENT PAPERHAVING A PHTOCONDUCTIVE INSULATIVE COATING ON ONE SIDE THEREOF THAT ISPHOTOELECTRICALLYRESPONSIVE WHEN SUBJECTED TO AN ELECTRICAL CHARGE,WHICH COMPRISES POSITIONING A POSITIVE TRANSLUCENT MASTER ON SAID SHEET,IMPRESSING AN ELECTRICAL POTENTIAL ON OPPOSITE SIDES OF SAID MASTER ANDSHEET WHILE IN CONTACT WITH EACH OTHER, DIRECTING ILLUMINATION THROUGHSAID MASTER TO THE PHOTOCONDUCTIVE SIDE OF SAID SHEET, THEREBY PRODUCINGAN ELECTRICAL CHARGE PATTERN CORRESPONDING TO THE COPY ON SAID MASTER,AND DEVELOPING SAID COATING BY APPLYING DEVELOPER TO SAIDPHOTOCONDUCTIVE SIDE.